What signal do we use while taking out our car (in a reverse gear) from parking lot?

Other than your reversing lights you mean.
Assuming you are looking behind you then simply complete the manoeuvre there are no further signals.
.

None is required.

None.

Just remember YOU have to yield to all traffic on the road because they have the right of way.

Your car, has back up lights. (a back up beeper added is always nice)

But no other signal. You have to watch all directions, and anyone else, has right of way